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85 lines
2.3 KiB
Go
85 lines
2.3 KiB
Go
10 years ago
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package main
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import (
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"crypto/md5"
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"encoding/binary"
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"fmt"
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"os"
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"sync/atomic"
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"time"
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)
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// RequestId is used for tagging each incoming http request for logging
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// purposes. The actual implementation is just the ObjectId implementation
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// found in launchpad.net/mgo/bson.
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type RequestId string
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func (id RequestId) String() string {
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return fmt.Sprintf("%x", string(id))
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}
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// Time returns the timestamp part of the id.
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// It's a runtime error to call this method with an invalid id.
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func (id RequestId) Time() time.Time {
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secs := int64(binary.BigEndian.Uint32(id.byteSlice(0, 4)))
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return time.Unix(secs, 0)
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}
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// byteSlice returns byte slice of id from start to end.
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// Calling this function with an invalid id will cause a runtime panic.
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func (id RequestId) byteSlice(start, end int) []byte {
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if len(id) != 12 {
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panic(fmt.Sprintf("Invalid RequestId: %q", string(id)))
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}
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return []byte(string(id)[start:end])
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}
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// requestIdCounter is atomically incremented when generating a new ObjectId
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// using NewObjectId() function. It's used as a counter part of an id.
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var requestIdCounter uint32 = 0
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// machineId stores machine id generated once and used in subsequent calls
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// to NewObjectId function.
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var machineId []byte
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// initMachineId generates machine id and puts it into the machineId global
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// variable. If this function fails to get the hostname, it will cause
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// a runtime error.
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func initMachineId() {
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var sum [3]byte
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hostname, err := os.Hostname()
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if err != nil {
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panic("Failed to get hostname: " + err.Error())
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}
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hw := md5.New()
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hw.Write([]byte(hostname))
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copy(sum[:3], hw.Sum(nil))
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machineId = sum[:]
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}
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// NewObjectId returns a new unique ObjectId.
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// This function causes a runtime error if it fails to get the hostname
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// of the current machine.
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func newRequestId() RequestId {
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b := make([]byte, 12)
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// Timestamp, 4 bytes, big endian
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binary.BigEndian.PutUint32(b, uint32(time.Now().Unix()))
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// Machine, first 3 bytes of md5(hostname)
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if machineId == nil {
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initMachineId()
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}
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b[4] = machineId[0]
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b[5] = machineId[1]
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b[6] = machineId[2]
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// Pid, 2 bytes, specs don't specify endianness, but we use big endian.
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pid := os.Getpid()
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b[7] = byte(pid >> 8)
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b[8] = byte(pid)
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// Increment, 3 bytes, big endian
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i := atomic.AddUint32(&requestIdCounter, 1)
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b[9] = byte(i >> 16)
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b[10] = byte(i >> 8)
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b[11] = byte(i)
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return RequestId(b)
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}
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